/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.FutureTask;

/**
 * A {@link FutureTask} that also implements the {@link ListenableFuture}
 * interface. Subclasses must make sure to call {@code super.done()} if they
 * also override the {@link #done()} method, otherwise the listeners will not be
 * called.
 * 
 * @author Sven Mawson
 * @since 2009.09.15 <b>tentative</b>
 */
public class ListenableFutureTask<V> extends FutureTask<V> implements
        ListenableFuture<V> {

    // The execution list to hold our listeners.
    private final ExecutionList executionList = new ExecutionList();

    /**
     * Creates a {@code ListenableFutureTask} that will upon running, execute
     * the given {@code Callable}.
     * 
     * @param callable
     *            the callable task
     * @throws NullPointerException
     *             if callable is null
     */
    public ListenableFutureTask(Callable<V> callable) {
        super(callable);
    }

    /**
     * Creates a {@code ListenableFutureTask} that will upon running, execute
     * the given {@code Runnable}, and arrange that {@code get} will return the
     * given result on successful completion.
     * 
     * @param runnable
     *            the runnable task
     * @param result
     *            the result to return on successful completion. If you don't
     *            need a particular result, consider using constructions of the
     *            form: {@code ListenableFuture<?> f =
     *     new ListenableFutureTask<Object>(runnable, null)}
     * @throws NullPointerException
     *             if runnable is null
     */
    public ListenableFutureTask(Runnable runnable, V result) {
        super(runnable, result);
    }

    public void addListener(Runnable listener, Executor exec) {
        executionList.add(listener, exec);
    }

    @Override
    protected void done() {
        executionList.run();
    }
}
